Biology subjects

Rahav, G.

Publications and source records attributed to Rahav, G..

5 recordsLinked to original sources

bioRxiv2024

Enterobactin and Salmochelin S4 inhibit the growth of Staphylococcus aureus

There is increasing demand for novel antimicrobial agents to tackle the antimicrobial resistance crisis. Here we report that two Enterobacteriaceae-produced siderophores, enterobactin and salmochelin S4, inhibit the growth of Staphylococcus aureus isolates, including methicillin-resistance S. aureus (MRSA) clinical isolates. The MIC50 for different S. aureus isolates were 2-5 M for salmochelin S4 and 5-10 M for enterobactin. This inhibitory activity was partially repressed by adding Fe+3. These siderophores also inhibited the growth of Enterococcus strains, including vancomycin-resistant enterococci (VRE) clinical isolates, though less effectively than for S. aureus. The growth of various Gram-negative bacteria was barely affected by these siderophores. These results shed new light on the role of enterobactin and salmochelin in bacterial physiology and ecology and have potential for the development of novel strategies to combat the rapid rise of multidrug-resistant bacteria.

microbiology↗

bioRxiv2023

Type VII secretion system and its effect on Group B Streptococcus virulence

GBS may cause a devasting disease in newborns. In early onset disease of the newborn the bacteria are acquired from the colonized mother during delivery. We characterized type VII secretion system (T7SS), exporting small proteins of the WXG100 superfamily, in group B Streptococci (GBS) isolates from pregnant colonized women and newborns with early onset disease (EOD) to understand better understand T7SS contribution to virulence in these different clinical scenarios. GBS isolates were obtained from colonized mother prior to delivery and from newborns with EOD. DNA was analyzed for T7SS genes. A mutant EOD strain (ST17) was created by knocking out the essC gene encoding a T7SS protein. Galleria mellonella larvae were used to compare virulence of colonizing, EOD, and mutant EOD isolates. 33 GBS genomes were tested, 17 EOD isolates and 16 colonizing isolates. The T7SS locus encoded 8 genes: essC, membrane-embedded proteins (essA; essB), modulators of T7SS activity (esaA; esaB; esaC) and effectors: [esxA (SAG1039); esxB (SAG1030). ST17 isolates encode two copies of the essC gene and esxA gene encoding putative effectors but were present only in 23.5% of isolates. In ST1 isolates three copies of esxA gene were identified, but in ST6 and ST19 isolates all T7SS genes were missing. EOD isolates demonstrated enhanced virulence in G. mellonella model compared to colonizing isolates. The 118659{Delta}essC strain was attenuated in its killing ability, and the larvae were more effective in eradicating 118659{Delta}essC infection. essC gene deletion was associated with reduced bacterial growth. We demonstrated that T7SS plays an essential role during infection and contributes to GBS pathogenicity. Author SummaryType VII secretion system (T7SS) is related to virulence in various bacteria but is not well characterized in Group B Streptococci (GBS). GBS may cause sepsis, meningitis, and death in newborns. The bacteria rarely cause disease in pregnant mothers. Newborns acquire GBS from the colonized mother during delivery. We studied the role of T7SS in GBS isolates obtained from newborns with GBS sepsis in the first week of life and in colonized pregnant mothers. By studying T7SS genes we discovered that the genetic structure of the T7SS differs between isolates causing severe disease and colonizing isolates. To study the virulence of different GBS isolates we injected them into larvae and monitored larvae survival. Isolates causing severe disease in the newborn caused a more severe disease in larvae compared to colonizing isolates. We then deleted T7SS genes in GBS isolates causing severe disease. The killing activity of GBS isolates without T7SS genes was attenuated. The larva responded to these bacteria similarly to the response found when injecting the larva with GBS isolates from colonized mothers. These results support our hypothesis that T7SS is important for causing severe infection in the newborn and that this system contributes to GBS pathogenicity.

microbiology↗

bioRxiv2020

Environmental shedding of toxigenic Clostridioides difficile by asymptomatic carriers: A prospective observational study

ObjectivesTo compare the burden of environmental shedding of toxigenic C. difficile among asymptomatic carriers, C. difficile infected (CDI) patients and non-carriers, in an inpatient non-epidemic setting. MethodsC. difficile carriage was determined by positive toxin-B PCR from rectal swabs of asymptomatc patients. Active CDI was defined as a positive 2-step EIA/PCR test in patients with >3 unformed stools/24 hours. C. difficile environmental contamination was assessed by obtaining specimens from 10 sites in the patients rooms. Toxigenic strains were identified by PCR. We created a contamination scale to define the overall level of room contamination that ranged from clean to heavy contamination. Results117 rooms were screened; 70 rooms inhabited by C. difficile carriers, 30 rooms by active CDI patients and 17 rooms by non C. difficile -carriers (Control). In the carrier rooms 29 (41%) had more than residual contamination, from which 17 (24%) were heavily contaminated. In the CDI rooms 12 (40%) had more than residual contamination from which 3 (10%) were heavily contaminated, while in the control rooms, one room (6%) had more than residual contamination and none were heavily contaminated. In a multivariate analysis, the contamination score of rooms inhabited by carriers did not differ from rooms of CDI patients, yet both were significantly more contaminated than those of none carriers OR 12.23 and 11.16 (95%CI:1.5-99.96 P=0.0195, and 1.19-104.49 p=0.035), respectively. ConclusionHere we show that C. difficile carriers rooms are as contaminated as those of patients with active CDI and significantly more than those of non-carriers.

microbiology↗

bioRxiv2019

Patterns and predictors of Staphylococcus aureus carriage during the first year of life; a longitudinal study

ObjectivesTo determine the patterns of S. aureus carriage in the first year of life, its determinants and dynamics of transmission between mothers and infants.\n\nMethodsProspective longitudinal cohort study of S. aureus carriage among mothers and their infants. Monthly screenings from pregnancy/birth through the first year of the infants life. Medical and lifestyle data was collected. Infant S. aureus carriage was detected by rectal and nasal swabs and maternal carriage by nasal swabs. Multivariate analysis and an NLMixed model were used to determine predictors of carriage and S. aureus persistence.\n\nResults130 S. aureus carrier women and their 132 infants were included in the study. 93% of the infants acquired S. aureus sometime during the first year of life, 64% of them acquired the maternal strain, mostly (66%) during the first month of life. 70 women (52.50%) and 17 infants (14%) carried S. aureus persistently. Early acquisition of S. aureus carriage was associated with longer duration of initial carriage and was the most significant predictor of S. aureus persistence, while day-care center attendance was negatively associated with persistent carriage.\n\nConclusionsEarly acquisition of S. aureus, mostly from the mother, is an important determinant of carriage persistence in infancy.

epidemiology↗

bioRxiv2018

Comparison of early effects of PCV7, PCV10 and PCV13 on S. pneumoniae (SP) nasopharyngeal carriage in a population based study; the Palestinian-Israeli Collaborative Research (PICR)

BackgroundPneumococcal conjugate vaccines (PCVs), PCV10 and PCV13, are currently used in different countries. We have previously reported the effectiveness of PCV7, following its introduction in Israel and before PCVs were introduced in Palestine. Here, we extended the study and compared the initial impact of PCV10 to that of PCV7/13.\n\nMethodsFour cross-sectional surveys of S. pneumoniae carriage among children <5y through 2009-2014 were preformed among two proximate populations, living under two distinct health authorities, with different vaccination policies. In East-Jerusalem (EJ), PCV7 was implemented in 2009 and replaced by PCV13 in late 2010, while in Palestine (PA), PCV10 was implemented in 2011.\n\nResultsA total of 1267 and 2414 children from EJ and PA were screened. Implementation of both PCV7 (in EJ) and PCV10 (in PA) did not affect overall S. pneumoniae carriage ([~]30%), but resulted in a significant decrease in carriage of VT7 strains. In the pre-vaccine era, VT7/VT13 strains consisted 47.0%/62.0% and 41.2%/54.8% of pneumococci in EJ and PA, respectively. A 48.6% and 53.9% decrease was observed within 3 years of PCV7 implementation in EJ (p= 0.001) and PCV10 in PA (p<0.0001), respectively. These vaccination policies also resulted in [~]50% reduction in VT13-added serotypes especially 6A (from 11.0% to 0.0% (EJ) and 9.5% to 4.9% (PA)). Three years after PCV13 implementation in EJ, an additional 67% decrease in VT13 strains was observed, yet an increase in serotype 3 was observed (0.0% to 3.4%, p=0.056). The prevalence of non-VT13 strains increased during the study period from 38% and 45.3% to 89.8% and 70.7%, in EJ and in PA respectively.\n\nConclusionsWithin the first three years following PCV implementation, we observed similar reductions in carriage of VT10 and VT13 strains with either vaccination policies, with no effect on overall carriage. Further follow-up is needed to compare the long-term effects.

microbiology↗